First off.. aren't the basic frameworks of keyboard-based rhythm games pretty similar?

You press the descending notes to match the judgment line. That's the basic idea, right? Even in different games, the same patterns appear frequently. This is Project Sekai on the left and Arcaea on the right, notice how similar the note patterns are? Since I've already experienced the one on the right, I can handle the one on the left with ease. If you want to improve your skills, don't be picky about songs and try a variety of them, or even better, trying out different games is a great method. However, since each game pursues a different playstyle, the pattern tendencies might not be exactly the same. If you were to ask me right now, "Then what rhythm game is most similar to Project Sekai?" I'd say Chunithm, not Arcaea.. It's not exactly the same, but the way they play with note sizes is similar.